High-income families are spending more time and money than ever on their children’s education, further widening the gulf between rich and poor students, according to a new report.

High-income families have always invested more in education, but they now spend seven times more a year on average than a low-income family, up from four times in the 1970s, according to the report, coauthored by MIT economics professor Michael Greenstone. These families now spend as much as $9,000 annually on private tutoring, SAT prep courses, computers, and other activities, compared with about $1,300 for low-income families.

The advantages that money can buy on tests and college applications have become so great that they threaten to undermine the American ideal of education as the great leveler that enables anyone who works hard to succeed, regardless of income level, the report said. In a knowledge-based economy that increasingly rewards education and skill, the report added, these growing educational disparities could further widen the income gap between rich and poor.

“The living standard in our country depends critically on getting more people to go to college,” said Greenstone, who is also the director at the Hamilton Project, the Washington think tank that issued the report. “The most concerning thing is that there are initial signs that inequality is starting to bleed into social mobility. And social mobility is at the heart of the American experience.”

The report is based on the analysis of several studies of education and income by economists and other researchers. Among its findings: Test scores of low-income students have shown only modest gains nationally during recent decades, while high-income students have shown large increases.

In addition, the report found, a student attending one of the nation’s most selective universities is 14 times more likely to be from a high-income family than a low-income one.

“Students from high-income families are pulling away from their low-income peers,” the report said. “College graduation rates have increased dramatically over the past few decades, but most of these increases have been achieved by high-income Americans.”

$9,000: Amount a high-income family spends annually on tutoring, SAT prep courses, and other activities; $1,300: Amount spent on similar goods and services by a low-income family

Research indicates that mothers with college degrees spend 4.5 more hours a week engaging with their children than mothers with a high school diploma or less, Greenstone said. By age 3, children of parents who are professionals have vocabularies that are 50 percent larger than children from working-class families, and 100 percent larger than the vocabularies of children whose families receive welfare.

Sharon Scott-Chandler, executive vice president of Action for Boston Community Development, or ABCD, said the report was “right on the mark.” The agency operates two alternative high schools and more than 100 community service programs for low-income families.

She said many low-income parents are working two and three jobs, either day or night or both, taking them away from their children. Many of these parents, and their children, believe college is unattainable, both financially and academically.

Many poor students never apply to private colleges even if they have done well in high school, thinking they are not qualified or cannot afford it, said Scott-Chandler.

“We have to constantly tell young children and those in their teens that you can go to college, it is the key to getting out of poverty and doing what you want to do in life,” she said. “We see families that figure out a way to keep their kids focused on college. Those are the families that are able to move out of poverty.”

The Hamilton Project report encouraged policy makers to provide additional federal grants to low- and middle-income students, but it also found that relatively simple, inexpensive policy changes could improve the educational attainment of poor children.

For example, said Greenstone, simplifying financial aid applications and providing low-income families help in filling them out could increase college enrollment by about 8 percentage points at a cost of less than $100 a student.

Another recent study found that mailing high-achieving, low-income students personalized information on their college options nudged students to apply to better schools.

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